Mass data storage and retrieval system providing multiple transfer paths with multiple buffer memories

ABSTRACT

A mass storage/retrieval module for controlling the storage and retrieval operations of massive amounts of data in peripheral devices such as tape, disk, optical, etc. provides for a buffer memory system in each of the interface control modules which permit simultaneous and concurrent writing to buffer storage and reading out of buffer storage through multiple ports for high rates of data transfer operations. Redundancy and high reliability is provided in that each module of the system has dual busses and live replacement units such that, upon failure, an alternate unit can carry the circuitry requirements until the failing unit has been replaced.

This is a divisional of copending application(s) Ser. No. 07/949,280,filed on Sep. 22, 1992, now U.S. Pat. No. 5,337,414.

FIELD OF THE INVENTION

This disclosure involves control systems providing configurations formass storage using various types of peripherals such as disk, tape oroptical drives.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is related to applications U.S. Ser. No. 898,633 filedJun. 15, 1992, entitled Universal Power Distribution System, and U.S.Ser. No. 948,381, filed Sep. 21, 1992 entitled "Multiported BufferMemory System for Disk Drive Complex" which applications are includedherein by reference.

BACKGROUND OF THE INVENTION

Continued development and upgrading of magnetic disk subsystems lead tothe desirable features of higher performance, greater capacity, higherreliability, more connectivity, in addition to reduced powerconsumption, reduced footprint area, and reduced heat dissipation.

As seen in FIG. 1B, the general block diagram of the present massstorage and retrieval system would include a host processor 4 forseveral interface modules such as channel interface module 8_(c) (CIM)and device interface module 8_(d) (DIM) connected to a plurality of diskdrive units 70 or other types of peripheral storage devices. Theparticular interfaces in various types of mass storage systems will varyaccording to the individual design of the manufacturer. In the presentdescribed architecture, the interfaces involve two particularlyefficient interfaces known as the channel interface module 8_(c) whichuses the later described buffer memory of the mass storage system andalso a device interface module (DIM) 8_(d) which also uses the hereindescribed buffer memory system configuration.

In the prior art and other conventional memory systems, where buffermemories were used in interfaces for Read, Write, and other operationsin mass storage systems, the requirement of time multiplexing of thememory caused undesirable wait periods for accessing by the numeroussources which had to access the memory.

As an example, buffer memories would normally be accessed by varioussources such as a host processor, a control processor, and by variousdata channels which communicated to a series of peripheral storageunits. It was the problem of delay and of waiting for taking of turnsfor each of these particular outlying sources in accessing the buffermemory, that created and caused unacceptable delays.

When dual port buffer memories were used, this not only increased thecost, the amount of board surface involved, but also increased powerusage on the board in addition to causing contention between the twoports of each memory. Even in this case, there were two sources ofaccess which still had to wait for their turn for memory access andattention.

In order to reduce the use of power consumption and to reduce the amountof board surface required and especially to keep the simplicity as wellas the "fairness of access" to all of the sources available, the presentarchitecture for a storage and retrieval system providing massive datastorage having rapid access and retrieval on a simultaneous andconcurrent basis using multiple peripheral storage devices, has beendesigned to overcome the aforementioned limitations. Further, redundancyof buses, power supplies and faulty module replacement without shutdown,allows uninterruptible access to stored information.

GENERAL OVERVIEW

A more highly efficient and less costly data storage and retrievalsystem for mass storage is indicated in FIG. 1B. FIG. 1A shows one-halfof the overall system in order to illustrate the flexibility andoperability. A complete mass storage configuration would include twicethe number of CIM and DIM controller boards shown in FIG. 1A.

As seen in FIG. 1A, there are four controller boards, two of which(8_(c1), 8_(c2)) are the channel interface module (CIM) controllerboards which use a specialized multiported buffer, and there is alsoshown in FIG. 1A two device interface module (DIM) controller boards(8_(d1), 8_(d2)) which also use the specialized multiported buffer.

A fully configured system would have eight interface controller boardsso that in FIG. 1A there would be four channel interface module boards(CIM) and four device interface module (DIM) boards.

Within each of the eight controller boards (of which four are shown inFIG. 1A), there is seen the buffer memory systems 24_(c1), 24_(c2), and24_(d1), and 24_(d2)) wherein each of these buffer memory systems havefour ports designated as P₀, P₁, P₂, and P₃.

As will be described hereinafter, all the individual memory modules usedin the multiported buffer memory are single ported static RAMs which arecheaper yet more dense and smaller in terms of usable space thanmultiport static RAMs.

The presently described mass data storage system consists of a family ofstand alone data storage systems. These are attachable to certain UnisysCorporation host systems by means of a fiber channel interface and blockMUX channel (BMC) and (IPI) intelligent peripheral interface or by anindustry standard small computer systems interface (SCSI).

Each individual sub-system is self-contained within a single cabinet andmay consist of a unit called a Control Module Rack (CMR) and from 1 to 8Data Storage Racks (DSR) which may be any combination of magnetic disk,optical disk, cache memory, or even magnetic tape based storage units.

Various functional control module rack (CMR) configurations permit anycombination of Channel Interface Modules (CIM) and Device InterfaceModules (DIM), configured up to a maximum of 8 separate modules.

A configuration of 4 CIMs and 4 DIMs will provide 8 host ports and 16SCSI buses.

Data storage capacity (unformatted) for the "disk-only" version isexpandable from a basic 2.3 gigabytes (single disk drive) to 128gigabytes (56 dual ported disk drives configured with seven drives perdual SCSI bus.

Additionally, the disk-only option can be arranged to support a RAIDtechnology which functions as a redundant array of inexpensive disks.This can be done in the RAID space "0" (Simplex) and also in a RAID 3and modified RAID 5 (parallel array) configuration.

The presently described mass storage subsystem has the capability forfully redundant operation and is provided with "live replacement"modules for all subsystems such as the power system, power controlsystem, data channels and storage devices. This permits virtuallyuninterruptible access to stored information. Thus data loss in such aredundant configuration is virtually eliminated.

The CMR or Control Module Rack contains all the hardware logic requiredto manage and control the data storage and the mass storage subsystem.The Control Module Rack is a fully self-contained rack module whichholds the following modular components. (i) two power supplies (AC toDC); (ii) channel interface modules (CIM); (iii) device interfacemodules (DIM); (iv) Futurebus Central Arbiter Module, (two each); (v)Futurebus Backplane Assembly.

A total of eight standard CIM and DIM modules can be mounted in theControl Module Rack.

The interface control logic modules designated as the CIM and the DIMare located in the Control Module Rack and communicate with each otherby means of the industry standard IEEE Futurebus Plus Interface. The CIMmodules provide communication to the Host System via a fiber channelinterface using the federal standard FIPS 97 protocol (FederalInformation Processing Standards Protocol), or BMC (Block MultiplexerChannel) or IPI (Intelligent Peripheral Interface) or via the industrystandard SCSI interface.

The device interface modules (DIM) provide control and communicationwith the data storage devices in the Data Storage Rack (DSR) by means ofthe industry standard SCSI-2 Interface. All of the active components andmodules of the control module rack (CMR) are designed for livereplacement together with full fault notification to the host system topermit on-line maintenance capability.

Power regulated DC power (for the CIM/DIM modules located in the ControlModule Rack) are provided by two AC-DC power converter modules. Thesepower modules operate as a parallel redundant pair, normally sharing thepower load of the Control Module Rack.

In the event of failure of either power module the other power moduleautomatically assumes the full load of the Control Module Rack untilreplacement of the faulty module can be affected. Failure information isalso sent to the host system to alert it that module replacement isrequired. The "live replacement" capability of the power modules assuresthat there will uninterrupted operation of the control module rack CMRin the event of a power module failure without need to shutdown thesystem.

The Futurebus Backplane Assembly consists of two 32-bit wide, fullyindependent backplane data buses, each having associated Futurebuscontrol bus lines. In the event of a fault on one of the buses, controlprocessor (in each CIM, DIM) will automatically reconfigure in order toutilize single bus operation and continue to operate even though in areduced band width mode. Within the Channel Interface Module (CIM),there is provided a Fiber Channel Interface Module which providescommunication with the host system by means of a fiber channelinterface. Two simultaneously usable channel connections are provided asstandard operating functions. Communications with other channelinterface modules (CIM)and other device interface modules (DIM) withinthe mass storage subsystem is done using the industry standard FuturebusInterface.

In addition to providing host communication functions, the CIM modulealso provides control and management of the Futurebus interface andmanagement of all commands issued through its fiber channel interface.The connection between a host and a peripheral data storage deviceduring execution of a command, is defined as a "logical path".

A "logical path", within the subsystem segment, consists of a CIM moduleand a DIM module, interconnected by the Futurebus Backplane Assembly,and the connection from the Device Interface Module (DIM) to theperipheral storage devices via the SCSI-2 Interface Bus.

An alternative or optional additive type of channel interface module(CIM) is designated as the SCSI channel interface module. This moduleprovides communication with the Host System 4 via the industry standardSCSI-2 interface. Two channel connections are provided as standard.Other functions of the SCSI-CIM are identical to that of the fiberchannel version of the channel interface module (CIM).

The disk device interface module (DIM) provides communication, in a RAIDSimplex mode, with the data storage devices connected to the massstorage subsystem by using the industry standard SCSI-2 interface. FourSCSI interface connections are provided as a standard. Communicationwith other CIM and DIM modules within the mass storage subsystem is doneusing the industry standard Futurebus Interface.

In addition to providing device communication functions, the DIM modulealso provides control/management of the Futurebus Interface andfunctions as a Host Adaptor and a SCSI Initiator for all receivedcommands. Each individual Disk Device Interface Module (DIM) canfunction as a magnetic disk control or as an optical disk control. Thefunctional characteristics involved are determined by the DIM microcode,which is downloadable from the Host System via a CIM/Futurebusconnection.

One configuration of the device interface module (DIM) is designated asthe RAID device module which provides communication, in a RAID 3 ormodified RAID 5 mode, with magnetic disk data storage devices within thesubsystem by means of the industry standard SCSI-2 interface.

The use of the RAID-DIMs require additional space within the controlmodule rack (CMR) above the space required for a standard deviceinterface module (DIM).

The Data Storage Rack (DSR) or Disk Data Storage Rack contains all thehardware required for installation and support of a disk type datastorage module in the subsystem. The control module rack (CMR) is afully self-contained rack module which consists of the followingcomponents: (i) two power supplies; (ii) magnetic disk data modules(MDM) which may involve from 1 to 7 units; (iii) optical disk datamodules (ODM), one, two, or four, depending on size; (iv) a SCSI-2 busbackplane assembly.

A total of 7 MDM or ODM modules in any combination can be mounted in thedata storage rack (DSR).

The Data Modules (MDM and ODM) in the data storage module (DSR)communicate with the DIMs in the control module racks (CMR) by means ofthe industry standard SCSI-2 interface. Each Data Module has dual SCSI-2ports and can communicate with two DIM modules via dual SCSI-2 buses.

Two fully independent SCSI-2 Bus subsystems are implemented within eachdata storage rack DSR. Regulated DC power is provided by redundant powersupplies to all the data modules in the data storage rack. Again, allactive components and modules are designed for live replacement withoutshutdown with full fault notification to the host system to permiton-line maintenance capability.

The SCSI-2 Bus Backplane Assembly (SBA) consists of the printed circuittype of backplane having two SCSI-2 buses and a power distribution bus.In event of a fault on one of the SCSI-2 interface buses, a controlprocessor in each CIM and DIM module automatically reconfigures that buspair for single port operation and continues to operate in a reducedcapability mode. The SCSI-2 bus interfaces are contained within the datastorage rack (DSR).

The Magnetic Disk Data Storage Module (MDM) consists of one 51/4 or 31/2inch extended form factor, dual ported SCSI-2 magnetic disk drive. Thisdrive module is physically and electrically configured for "liveinsertion" into the SCSI Bus Interface Module Backplane. No cables arerequired. Up to 7 data storage modules may be installed in a datastorage rack (DSR).

Using 8 data storage racks this would provide a total of 56 magneticdisk storage modules for a full configuration. This live replacementcapability of a data storage module assures uninterrupted operation of adata storage rack in the event a module must be replaced.

The power distribution module (PDM) of the system consists of dualindependent Power Distribution Units (PDU) which are mountable orremovable within the cabinet. The PDM has two independent AC Power InputCables, one for each power distribution unit (PDU).

Remote power sequencing and emergency power-off capability (inaccordance with FIPS 61) is also provided for the data storage rack(DSR). All active components in the power distribution module (PDM) havelive replacement capability together with full fault notification to thehost system for uninterrupted operation.

The Power Distribution Unit (PDU) provides control, fault monitoring anddistribution of AC Power to the various modules within the cabinet.Regulated DC power and also low voltage AC power for the control unitand FIPS-61 modules are also provided. In the event of failure of eitherpower distribution unit (PDU), then the other PDU will automaticallyassume the full load of this subsystem until replacement of the faultymodule can be effectuated. This live replacement capability assuresuninterrupted operation in the event of a power component failure. EachPDU has a Control Module which provides sequence control functions andfault monitoring for the power distribution unit (PDU).

In the presently described embodiment, the buffer memory system isprovided with four ports of 36-bits data width. Each and every one ofthe ports can access the entire memory in each of the memory modules ofthe buffer memory system.

Operationally the maximum wait period for any first access is 350nanoseconds and then the access to the next following data words will beoperable at 80 megabytes per second for the entire burst size. The burstsize can be from one word to a maximum of the entire size of the memorysystem modules which is 64 megabytes.

With the use of a multiport memory system in which the describedembodiment of FIG. 1A shows four ports, the information in the buffermemory system is shared between a control processor (10_(c1), 10_(c2),10_(d1), 10_(d2)) and two Future bus interfaces 31, 32 (FB1, FB2) plusthe interface processors such as IP_(c1), IP_(c2), IP_(a1), IP_(d2))which respectively provide interfaces to the host computer and to thedevice interfaces for the multiple peripheral storage devices.

As seen in FIG. 2, the buffer memory system is shown in more detail inconjunction with one controller board that is to say, the DIM deviceinterface module controller board 8a. Each of the ports P₀, P₁, P₂, P₃of FIG. 2 (26, 27, 28, 25) has a transfer capability of 80 megabytes persecond. FIG. 3 shows a block diagram of the internal elements of thebuffer memory system. The use of address-transfer VLSI circuits (24_(a))and data transfer VLSI circuits (24_(d)) are operable to reduce thepower requirements of the system as well as the amount of board spaceand cost.

Each of the ports P₀, P₁, P₂, and P₃ is capable of handling 27-bits ofAddress Bus, 36-bits of Data Bus, and 6-bits of Control Bus.

There are four memory modules in FIG. 3 (24_(m0), 24_(m1), 24_(m2),24_(m3)) which are addressed with the least significant bits of portaddresses such that module 0 will hold all addresses ending in 00,module 1 will hold all addresses ending in 01 and module 2 will hold alladdresses ending with 10 and module 4 will hold all addresses ending in11.

The buffer memory system interconnections are shown in FIG. 4 where eachmemory module is seen to be connected to a port no matter what thestatus is of that port. This provides for equal access (fairness) to allports within four system cycles wherein each system cycle takes a periodof 50 nanoseconds.

FIG. 5 shows the Address Transfer Logic (VLSI) portion 24_(a) of thebuffer memory system. It is seen that the address of each port is keptseparately in a counter (C₀, C₁, C₂, C₃) which will then multiplex thisaddress into each of the other module address ports. For one systemcycle, the module addresses are all kept within each of the multiplexerunits 24_(x0), 24_(x1), 24_(x2), 24_(x3)) shown in FIG. 5.

FIG. 6 shows the Data Transfer Logic portion (VLSI) 24_(d) of the buffermemory system. It will be noted that there are two independent paths foreach port making it possible to individually read or to writesimultaneously into the buffer at the same time.

Each one of the bus interface input/output units (24_(t), 24_(i))(BI-I/O) will be stable for at least one system cycle.

Each memory module (24_(c), 24_(d)) is made up of four virtual moduleunits constructed as shown in FIG. 7. To hold a capacity of fourmegabytes of 36-bit words, there are used nine static RAM chips, each ofwhich is 256K×by 4 bytes. Thus the nine RAM chips provide 262,144 wordsof 36 bits each per virtual module for a total of 1,048,576 words of 36bits each. Here, the 1,048,576 words of 36 bits each is the equivalentof 4,194,304 bytes (4 megabytes).

SUMMARY OF THE INVENTION

A single host computer or multiple numbers of host computers may beconnected to control module interfaces which permit high speed storageof masses of data on various types of peripherals such as disk drives,optical drives and/or tape drives.

The control module interfaces include a channel interface module (CIM)which interconnects to the host system for taking communications fromthe host system and transferring them across an internal bus to aperipheral device interface module (DIM).

The peripheral device interface module (DIM) is used to communicatebetween the physical data storage peripheral devices involved and theinternal bus (Futurebus) connecting the device interface module and thechannel interface module (CIM).

Each of the controller boards involving the channel interface module(CIM) and the device interface module (DIM) include high speed transfermulti-ported buffer units which permit the storage and transfer of data,both simultaneously on a Reading and Writing basis such that themultiple number of ports in a buffer memory system, within eachcontroller board, permit access to a multiple number of memory modulesin the buffer memory system.

Thus within each one of the CIM and the DIM control modules, themulti-ported buffer memory within each controller module permitssimultaneous and concurrent writing storage of data while at the sametime reading out of stored data. Within each of the buffer memory systemmodules (of which there are a multiple number M of modules), the systempermits any one of the four input ports to the buffer memory system toaccess any one of the multiple number of memory modules within thebuffer memory system for carrying out the functions of simultaneouslyreading out data and writing in data on a continuous basis.

The mass data storage system is made up of a number of individualsubsystems where each subsystem is self-contained within a singlecabinet and this cabinet consists of one Control Module Rack (CMR) andfrom one to eight Data Storage Racks (DSR) which house any combinationof magnetic disk units, optical disk units, cache memory or magnetictape base storage units. The subsystem is so arranged that it has thecapability of fully redundant operation such that, during operations, itis possible to replace any module in any of the subsystems withoutinterrupting the data transfer operations or the access to the storedinformation. Thus data loss in such a redundant configuration ispractically eliminated.

Additionally, a plurality of power supplies for the control module rack(CMR) is provided so that they operate as a parallel redundant pair ofpower supplies which share the power load. And in the event of failureof either module, the other power module will automatically assume thefull load of the control module rack (CMR) until replacement of thefaulty module is effectuated.

The present invention also provides a large capacity buffer memory offour memory modules which permit exceedingly rapid transfer of data andsimultaneously permit the Reading and Writing of data into and out ofthe memory modules from any one of the four ports of a multiport memorysystem.

In the preferred embodiment the multiport buffer memory system providesa port to a control processor, a port to a plurality of peripheralstorage devices/or host computer, and two ports to buses which connectto other channel interface (CIM) and device interface (DIM) modulespermitting data communication to and from a host processor and to andfrom a multiplicity of peripheral storage devices.

The four ports of the buffer memory system are connected to an addresstransfer logic system which permits access to each and every one of fourmemory modules in the system. Additionally a data transfer logic systemconnects to each one of the memory modules in order to permit thesimultaneously Reading out of, and Writing into, of data words, whilethe four ports provide interface connection to a host system and also toa multiple set of peripheral storage modules.

System cycles are operative so that during any one system cycle, therecan be one access allowed from any port to any buffer memory module.However, while this one access is occurring on one system cycle, duringthe next system cycle there can be another access for either a Readoutor a Write-in operation of a data word. The overall effect is thatconcurrently there is the continuous capability and flow of access toany one of the buffer memory modules from any one of the four ports ofthe buffer memory system. This insures an equality of access for eachand every one of the ports to a desired buffer memory module and alsoinsures that there can be simultaneous action cycles occurring both forthe Read-out of data and for the Writing-in of data from any one of themultiple ports.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a disk mass storage and retrieval systemshowing one-half of a typical system where there is seen two channelinterface modules and two device interface modules which connect thehost processors of the system to a plurality of disk drive modules.

FIG. 1B is a simplified block diagram of the overall mass storagesystem.

FIG. 2 is a diagram of the device interface module and its internalusage of the multiported buffer memory system;

FIG. 3 is a block diagram of the buffer memory system showing thevarious elements involved;

FIG. 4 is a interconnecting diagram showing how the buffer memorymodules are interconnected to the four ports involved in the buffermemory system;

FIG. 5 is a more detailed diagram of the address transfer system of thebuffer memory using buses and VLSI circuitry;

FIG. 6 is a more detailed block diagram showing the elements of the datatransfer logic of the buffer memory system;

FIG. 7 is a schematic drawing showing the arrangement of RAM chips toform the four-module buffer memory system;

FIG. 8 is a drawing showing the relationship between the four ports andthe four buffer memory modules during each of a sequence of systemcycles;

FIG. 9 is a drawing showing the time sequence wherein various addressesinteract with the four memory modules of the buffer memory system inperforming access-Read operations.

FIG. 10 shows the access Write function during a period of system cyclesshowing the relationship between the address, the time period involvedand the various functions in each of the four memory modules;

FIG. 11 is a flow chart showing the function of the overall systemduring a Read and Status operation;

FIG. 12 is a flow chart showing the various steps involved in the systemfor a Write and Status operation.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring to FIG. 1A there are shown four controller boards which areillustrative of one-half of the overall system. The normal system wouldhave eight such controller boards located in a single cabinet.

As seen in FIG. 1A, the two upper controller boards are modulesdesignated as the channel interface module (CIM) and are shown aschannel interface module 8_(c1) and 8_(c2).

The two lower controller boards are designated as device interfacemodules (DIM) and are indicated as device interface modules 8_(d1) and8_(d2).

Referring to the channel interface modules 8_(c1) and 8_(c2), there willbe seen two protocol chips designated I-1 and I-2 which communicate tothe main host processor 4 (or alternatively there can be communicationto four separate host processors which could be designated 4_(a), 4_(b),4_(c), and 4_(d)). The protocol chips (I-1, I-2) can be designated asblock multiplexor channel host interface protocol chips. These functionto communicate data and to transfer commands and status information toand from the host processor 4. The first set of protocol chips I-1 andI-2 are under control of the interface processor designated IP_(c1). Theinterface processor, IP_(c1), controls the protocol chips I-1 and I-2 sothat the interface processor (IP_(c1)) can independently act in order toprovide an appropriate "fair share" of buffer access time to each one ofthe set of two protocol chips I-1 and I-2.

Likewise, the interface processor IP_(c2) is also a processor whichoperates as a hardware state machine and also provides the function toinsure there will be a fair share of access time between the buffer 24and each of the protocol chips I-1 and I-2 in its communication to andfrom the host computer 4.

The interface processor (such as IP_(c1) and IP_(c2)) communicatesrespectively to the buffer memories 24_(c1) and 24_(c2). These buffermemories are used to store information data, control data, and statusdata during the operation of the system when data is being transferredbetween the host computer 4 and a series of peripherals such as diskdrive units 70_(a), 70_(b), 70_(c), 70_(d). These disk units 70_(a)through 70_(d) each represent multiple numbers of disk drive units.

The buffer memory units 24_(c1) and 24_(c2) are respectively controlledby the control processors 10_(c1) and 10_(c2), which also monitor thedual busses 6_(a), 6_(b) through state machines 31, 32 (FB1, FB2, FIGS.1A, 2) for operability so that a malfunction in one bus will cause thecontrol processor 10, FIG. 2, to channel data through the operable bus.

As indicated in FIG. 1A, the buffer memory (such as 24_(c1), 24_(c2))will have four ports where the Port P1 connects to the Futurebus statemachine (FB1) 31; the Port P2 communicates with the second state machineFB2, 32; the third port P3 of the buffer memory 24 communicates with theinterface processor IP_(c2) and the fourth port P0 communicates with thecontrol processor 10_(c2).

The Futurebus interface state machines (31,32) designated FB1 and FB2function to communicate between the channel interface modules (8_(c1),8_(c2)) and the device interface modules (8_(d1), 8_(d2)).

The connective arrangements to the Futurebus interface state machines 31and 32 are such that two sets of buses designated as 6₁ and 6_(b) willbe seen to interconnect the channel interface modules (CIM) with thedevice interface modules (DIM) in such a fashion that any channelinterface module (CIM) can talk to anyone of the device interfacemodules (DIM) thru the Futurebus state machines 31 and 32 (FB1 and FB2).

Again referring to FIG. 1A, the lower control boards 8_(d1) and 8_(d2)are the device interface modules (DIM) which also have buffer memoryunits 24_(d1) and 24_(d2) respectively controlled by the controlprocessors 10_(d1) and 10_(d2).

The buffer memories 24_(d1) and 24_(d2) will be seen to have connectionsto the interface processors IP_(d1) and IP_(d2) which are used tocommunicate with and handle data transfer operations by means of deviceprotocol chips D1 (D_(1a), D_(1b), D_(1c), D_(d1) FIG. 1A). The deviceprotocol chips, D1, are used to communicate to the disk drives 70₁,70_(b), 70_(c), and 70_(d) in order to transfer commands, data, andstatus information between the disk units 70 and the buffers 24_(d1) and24_(d2). Likewise also the chips D1 (D_(1a), D_(1b), D_(1c), D_(1d),FIG. 1A) can be arranged to communicate with tape or optical diskstorage means.

Operationally, FIG. 1A illustrates how the host processor system 4 canaccess information and data from the seven disk drives of 70_(a) or theseven disk drives of 70_(b), or 70_(c) or 70_(d).

The host 4 will send a command through the interface protocol chips suchas I-1 or I-2. The interface processor (IP_(c1), IP_(c2)) will conveythis command to the buffer memory (241, 24c2.sub.). The controlprocessors 10_(c1) or 10_(c2) will execute the command and will send thecommand through the Futurebus state machines 31, 32 (such as FB1 or FB2)to the device interface module (DIM) and its buffer memories (such as24_(d1) and 24_(d2)) for temporary storage.

The control processor (such as processor 10_(d1) or 10_(d2)) looks atthe transmitted command from the host, and selects which one of the FIG.1A device interfaces, D1 (D_(1a), D_(1b), D_(1c), D_(1d)), of the deviceinterface protocol chips will be used for access to send the command toa selected disk drive or other peripheral unit so that information canbe accessed from the disk drive and returned through the device protocolinterface D1 and into the DIM buffer 24_(d1) to 24_(d2). The controlprocessor (10_(d1) or 10_(d2)) will transfer this data from the diskthrough the Futurebus state machines (31, 32) up to the CIM buffers(24_(c1) or 24_(c2)). Then the interface processor (IP_(c1), IP_(c2))will transfer this data up to the host system 4, thus completing thefirst action of data transfer, which may be a READ operation or a WRITEoperation.

After this first activity is completed, then the disk drives, such as70_(a), 70_(b), etc. will provide "status data" back to the host 4through the same series of channel steps, that is to say, through thedevice protocol interface, D1, then through the interface processorIP_(d1) then through the buffer 24_(d1), then through the Futurebusstate machines 31, 32 of the DIM module 8_(d1), then by CIM module8_(c1), via the buffer 24_(c1) and to the interface processor IP_(c1)and thence through the interface protocol chip (I-1 or I-2) to the hostsystem 4.

Referring to FIG. 2, there is seen a block diagram of the controllerboard 8_(d) on which is patterned on the device interface module, DIM(indicated as 8_(d1) and 8_(d2) of FIG. 1A).

The control processor 10, FIG. 2, controls the execution of commandsreceived from the host 4 and operates upon the buffer memory 24. Thecontrol processor 10 is supported by the code SRAM 16 which providesmicrocode for the control processor 10 and is supported by the FAST SRAM18 which provides a working scratchpad area for the processor 10. TheFLASH EPROM 20 is a boot memory for starting up and for the diagnosticoperations used by the processor 10.

The control processor 10 has a data bus 12_(d) which connects to thebuffer memory 24, to the device protocol interfaces D1_(p), D2_(p),D3_(p), D4_(p), and also to the Futurebus state machines 31 and 32, tosense any malfunction in busses 6_(a), 6_(b) and to re-directcommunication through the properly operating bus. The device protocolinterfaces D_(1a), D_(1b), D_(1c), D_(1d) of FIG. 2 correlate to theinterfaces D1 of FIG. 1A.

The bridge logic 14 (FIG. 2) is a group of logic gates used to connectthe data bus 12_(d) and the instruction bus 12_(i).

The DIM controller board 8 shown in FIG. 2 also indicates that thebuffer memory 24 of the DIM 8 has four basic input/output port areasshown as 27, 28, 25 and 26. (These correlate to ports P₁, P₂, P₃, P₀FIG. 1A). The interface ports 27 (P1) and 28 (P2) provide busconnections to the futurebus state machines 31 and 32. The buffer portinterface 26 (P0) connects the control processor 10 via the data bus12_(d), FIG. 2. The buffer port 25 connects the buffer memory 24 to theperipheral units via device protocol chips D_(1a) thru D_(1d), FIG. 1Ato provide for channels of communication to the peripheral units 70_(p).

The futurebus state machine 31 (FB1) connects through the Futurebus-1(designated, 6_(a), to other channel interface modules (CIM). Likewisethe Futurebus state machine 32 connects via the bus 6_(b) in order tocommunicate to other device interface modules or DIMs.

The control processor 10 of FIG. 2 may be implemented with an AMD 29000RISC processor and is functionally used to control the channel interfacemodule (CIM) and the device interface module (DIM).

The channel interface module 8_(c) (CIM) is architecturally the same asthe described DIM 8_(d) of FIG. 2, except that instead of the 4 (quad)ports D1 (D_(1a), D_(1b), D_(1c), D_(1d), FIG. 1A of the DIM), there aredual (2) ports (in the protocol ships I₁ and I₂) for connection by eachCIM bard to the host processors of the host system 4.

FIG. 3 is a block diagram showing the elements of the buffer memory 24previously discussed in FIG. 2.

The buffer memory 24 has a first portion block designated as AddressVLSI 24_(a). The Address VLSI block has 4 inputs from 4 address portsdesignated port 0A, port 1A, port 2A and port 3A which correspond, inFIG. 2, to the elements 26, 27, 28, and 25, and correspond in FIG. 1A toports P₀, P₁, P₂, and P₃.

The Address VLSI module 24_(a) provides addressing connections to thefour memory modules 24_(m0), 24_(m1), 24_(m2), and 24_(m3). Thesemodules are also designated as memory module 0, 1, 2, and 3, and arestatic RAMs which are generally designated as SRAM's. Each of thesestatic RAMs will hold 128K×36 bits of memory information.

Then, as noted in FIG. 3, there are a series of output two way databuses B_(d1) connecting each of the four static RAM modules to the DataVLSI module 24_(d). The Data VLSI module 24_(d) is made of two chipswhich perform the function of multiplexing data to the memory module. Aseries of data ports 0D, 1D, 2D, and 3D are provided to both take in andput out data to the Data VLSI module 24_(d). In FIG. 2 these four portsare designated as D_(1a), D_(1b), D_(1c) and D_(1d) and they provide forthe interchange of data between the peripheral storage units (diskdrives 70) and the buffer memory module 24.

The incoming address buses in FIG. 3 are designated B_(a1) and each oneof the four buses carries a 27 bit address. The Address VLSI module 24which receives the data on the buses Bax is a module which is made ofone VLSI chip which provides a multiplex function for simultaneouslyaddressing the various memory modules such that any one of the addressports 0A, 1A, 2A, 3A, can operate to address each one of the four memorymodules 0, 1, 2, 3. The addressing from the address module 24_(a) isdone by means of the address buses B_(a2).

Data which resides (FIG. 3) in the four memory modules 0, 1, 2, and 3(24_(m0), 24_(m1), 24_(m2), 24_(m3)) is connected by a set of data busesB_(d1) to the data module 24_(d). These data buses enable data to be"written" into any one of the four memory modules or to be "Read out"from any one of the four memory modules on a simultaneous or concurrentbasis. The data on any one of the data buses of FIG. 3 designatedB_(d2), can travel by means of the four data ports 0D, 1D, 2D, 3D, whichcorrelate to P₀, P₁, P₂ and P₃ of FIG. 2.

The data buses B_(d2) each carry 36 bits of data to or from the memorymodules 0, 1, 2, 3, for purposes of reading 36 bits of data or forwriting in 36 bits of data.

The four address ports 0A, 1A, 2A, 3A (also designated as 26, 27, 28,and 25) receive the addresses from the control processor 10 such thatany one or each one of the ports 0A, 1A, 2A, 3A, can address any one ofthe four memory modules 0, 1, 2, 3 (24_(m0), 24_(m1), 24_(m2), 24_(m3))concurrently in time.

In conjunction with the addressing of the various memory modules, it isalso possible, at the same time, for data to be entering the ports 0D,1D, 2D, and 3D (P₀ P₁, P₂, P₃) for purposes of writing into theparticular sections of the addressed modules 0, 1, 2, and 3, of FIG. 3.

Likewise, concurrently data can also be being read out of the modulesmemory 0, 1, 2, and 3 and sent via the Data VLSI module 24_(d) over tothe data output ports 0D, 1D, 2D, 3D also designed P₀, P₁, P₂ and P₃ onFIGS. 2 and 3.

It should be understood, for example, that while port 2A is providing anaddress to the Address VLSI 24., then at the same time, data can beentering for writing purposes on port 2D. For example, port P₂ (28), itshould be understood, has two aspects, i.e. 27 address lines (2A) and 36data lines (2D).

It is possible for any one of the four ports 0A, 1A, 2A, 3A to addressany one of the four memory modules 0, 1, 2, 3 concurrently andsimultaneously while at the same time data is being written into or readfrom any particular ones of the memory modules 0, 1, 2, 3 by means ofdata transfers through the Data VLSI 24d. For example, each of the fourports 0D, 1D, 2D, and 3D can be writing to the same module, for example,as module 2, concurrently in order to write in data at separate or samelocations in module 2 (24_(m2)).

This is permissible since there can be four simultaneous addressesappearing on ports 0A, 1A, 2A, 3A, in order to tag or locate the speciallocation in module 2 where the writing of data is to be done.

Another example of the buffer memory system flexibility is that, forexample, there may be two Reads and two Writes occurring at the sametime involving each of the four memory modules 0, 1, 2, and 3, the onlylimitation being that each port 0A, (address) and port 0D datainformation occur simultaneously. Similarly, the addressing through theport 2A to the memory module 2 (24_(m2)) must be simultaneous with thedata port 2D (28), holding the 36 bit data word.

It should be understood that each combination of "address" and "data"port is an independent operable entity. Thus, operationally, any portcan access and address any location in any one of the four memorymodules.

Likewise, any one of the data ports (0D, 1D, 2D, 3D) can accesslocations in any one of the four memory modules. The only limitation isthat there be a "concurrence" in time between the port addressinformation delivery and the presence of the data via its correspondingdata port.

Referring to FIG. 4, there is seen the four static RAM buffer modules 0,1, 2, 3, (24_(m0), 24_(m1), 24_(m2), 24_(m3)).

Each of the buffer RAM memory modules 0, 1, 2, 3 are addressed via thecounters C₁, C₁, C₂, and C₃ on the right hand side of FIG. 4. Thesecounters receive address information via one of the port connections tocontrol processor 10(P₀), interface processor port 25 (P3), Futurebusinterfaces 31 (FB1) via P₁ or 32 (FB2) via P₂. This information isplaced in a counter and the incoming address is distributed to each oneof four buses which are the memory address buses designated M₀, M₁, M₂,M₃. This arrangement permits the address from any given port such asport 0A, 1A, 2A, 3A, to be placed in each of the respective counters C₀,C₁, C₂, and C₃. Then each of these counters will provide the incomingaddress to each one of the buses M₀, M₁, M₂, and M₃.

In this fashion, every incoming address on every one of the ports may beconveyed to every single one of the individual memory modules 0, 1, 2,3, (24_(m0), 24_(m1), 24_(m2), 24_(m3)).

Likewise looking to the left-hand side of FIG. 4, it will be seen thatthe series of ports designated port 0D, 1D, 2D, 3D, each providecommunication lines for the entry or the exit of data information. Theseconsist of 36 bit data words. Each of the data input ports can convey aninput data word into a register involved with the particular port. Theregister for each port is designated as R₀, R₁, R₂, and R₃. Each of theregisters are arranged so that the data word may be conveyed to each andevery one of the four buses designated B₀, B₁, B₂, and B₃, so that whendata is being written into a memory module, it is possible for any oneof the ports to access any one of the addressed memory modules in orderto write in a 36 bit data word.

Likewise, the busses B₀ thru B₃ also operate for "Reading" operations sothat any data word accessed from any one of the memory modules 0, 1, 2,3, can then be transferred to any one of the four ports 0D, 1D, 2D, 3D,for export to the control processor 10, to disk drives 70, toFuturebusses 31, 32.

Thus it is possible, for example, such that memory module 1 (24_(m1))can be addressed through the address port 0A, and at the same time thedata port 0D can be writing in data into that addressed location inmodule 1 (24_(m1)).

Similarly and concurrently, address port 1A can be addressing a locationin memory module 1 (24_(m1)) at the same time that the data port 1D isenabling the read out of a data word from module 1 (24_(m1)) over to arequesting master such as control processor 10.

In FIG. 4, it will be noted that each memory module 24_(m0), 24_(m1),24_(m2), 24_(m3) is connected to each one of the four address ports 0A,1A, 2A, 3A, and likewise each memory module is connected to each one ofthe data ports 0D, 1D, 2D, and 3D.

Thus there can be concurrent or simultaneous operation of at least fouraction cycles taking place in the buffer memory 24. These four actioncycles can be any mixture of Reads and Writes such as two Reads and twoWrites or three Writes and one Read all occurring simultaneously.

It should be noted that the registers R₀, R₁, R₂, R₃, FIG. 4, arearranged such that each register will hold data which is either to bewritten in, or which is to be read out, and thus this data will beavailable to any one or each one of the four buses B₀, B₁, B₂, B₃, sothat this data can then be used by any one of the four data ports 0D,1D, 2D, 3D.

Referring to FIG. 5 there is seen more detailed drawing of the AddressVLSI block module 24_(a), previously shown in FIG. 3.

As was indicated in FIG. 2, there were four ports in the buffer 24 whichwere designated as 25, 26, 27, and 28 (P3, P₀, P₁, P2) and these portsare shown as indicated at the top of FIG. 5 showing the port address in.Each of the input buses (B_(a), B_(a0), B_(a1), B_(a2), B_(a3)) here areattached to a counter (C₀, C₁, C₂, and C₃). Each of these counters havefour connections which are fanned out to include each of fourmultiplexors, MUX 0, 1, 2, 3, designated 24_(x0), 24_(x1), 24_(x2), and24_(x3). Each of these multiplexors will hold the memory module addressreceived, for a period of one system cycle. Then the output of each ofthe multiplexors 0, 1, 2, 3, are passed on respectively to each of theSRAM memory modules 0, 1, 2, 3, (24_(m0), 24_(m1), 24_(m2), and24_(m3)).

Each address coming on each of the ports 0A, 1A, 2A, and 3A will beconveyed by the four buses in each port (0A, 1A, 2A, 3A) over to themodule ports designated as MUX 0, 1, 2, and 3 (24_(x0) -24_(x3)).

As the counters are incremented, that is to say, C₀, C₁, C₂, and C₃,then each particular MUX module interface (24_(x0), 24_(x1), 24_(x2),24_(x3)) will have a period of time called a "system cycle" in which aparticular address is available in that particular module interface.

Thus, at the first "system cycle", the module interface MUX0 will holdthe incoming address from port 0A. On the next (second) system cycle,the MUX0 will hold the address input to port 1A; on the third systemcycle, the MUX0 will hold the address from the port 2A; and on thefourth system cycle, the MUX0 will hold the address which was insertedat port 3A.

Likewise this sequence of available addresses occurs in the other moduleinterfaces MUX0, MUX1, MUX2, and MUX3.

The Address block module 24, in FIG. 5, will be seen to have a busoutput M0-M3 from each of the module interfaces (MUX0, 1, 2, 3,) over tothe four SRAM memory modules 0, 1, 2, 3. The connections are provided bythe address buses M₀, M₁, M₂, and M₃ of FIG. 4.

Thus it will be seen that there is a sequence of communications wherebyport 0A talks first to module interface MUX0 for one system cycle; thenport 0A talks to MUX1 for the next system cycle; and port 0A talks toMUX2 for the next system cycle, and then 0A talks to MUX3 for the nextsystem cycle.

While this is occurring, each of the other ports are subsequentlytalking to the next module interface in sequence. This will besubsequently shown in FIG's. 8A, 8B, 8C, and 8D.

The Data VLSI block module 24d of FIG. 3 is now shown in more detail inFIG. 6.

Referring to FIG. 6, the Data block module 24_(d) provides for one lowergroup of four bidirectional transceivers designated 24_(i0), 24_(i1),24_(i2), 24_(i3).

These bidirectional transceivers connect respectively to the ports shownin FIGS. 2 and 3 as 26, 27, 28, and 25 respectively, also designated P₀,P₁, P₂, P₃.

This means that the buffer memory 24 has ports reaching to the controlprocessor 10, host processor 4, the Future bus state machine 31 and theFuture bus state machine 32 for connection respectively to other channelinterface modules (CIM) and other device interface modules (DIM) asindicated in FIG. 2.

Referring again to FIG. 6 to the upper transceiver group, it will benoted that each of the bidirectional transceivers 24_(t0), 24_(t1),24_(t2), and 24_(t3), each have two buses allocated to them so that eachof the bidirectional transceivers have a READ bus and a WRITE busrespectively to the READ data logic unit 24_(dr) and to the WRITE datalogic unit 24_(dw). The logic units 24_(dr) (data read) and 24_(dw)(data write) are each provided for by a single chip unit which useslogic gates.

Each of these upper group transceivers 24_(t0), 24_(t1), 24_(t2),24_(t3) connect one of the static RAM modules 24_(m0), 24_(m1), 24_(m2),24_(m3), (Modules 0, 1, 2, 3) to a particular one of the bidirectionaltransceivers, 24_(t0) -24_(t3).

Each of the bidirectional transceivers 24_(t) and 24_(i) will be seen tohave a READ bus connected to the READ data logic unit 24_(dr) and alsowill have a WRITE bus connected to the WRITE data logic unit 24_(dw).

Thus it will be seen that it is possible for any one of the four ports25, 26, 27, 28 (of buffer 24 of FIG. 2) to be connected for either READoperations or for WRITE operations to and from any one of the memorymodules 24_(m0) 24_(m1), 24_(m2), and 24_(m3).

Referring to FIG. 7, there is seen a schematic drawing of nine chips ofstatic RAMs which are used to form the memory buffers 24 of FIG. 2 andalso the Modules 0, 1, 2, 3, designated 24_(m0) 24_(m1), 24_(m2), and24_(m3), of FIG. 3.

Each chip of the nine chips is a RAMchip of 256K ×4 bytes for a total offour megabytes for the total memory buffer 24.

The module address inputs shown in FIG. 7 are sourced from the MUXmodule interfaces 0, 1, 2, 3, (24_(x0) -24_(x3)) shown in FIG. 5.

The module READ/WRITE control lines are sourced from the Address VLSIcontrol unit 24_(a) of FIG. 5.

The two way buses from the buffer memory RAM chips, which carry the datawords show that the transceivers 24_(i0), 24_(i1), 24_(i2), and 24_(i3),of FIG. 6 are the connecting vehicles for the Data block module 24_(d)(FIG. 3) to the buffer memory modules 0, 1, 2, 3.

The designation 256K×4 on each chip represents the storage of 4 groupsof 256 thousand bits of data in each chip. Thus with 9 chips, there are9×4=36 bit words available on the 9 chips for a total of 1 megabyte ofdata where each byte represents 8 bits.

The 256K×36 represents that there are 256 thousand words of 36 bitseach. This represents a module of one megabyte.

The buffer memory of the presently described disk drive control systemprovides for a buffer access time of 50 nanoseconds from any one of thefour ports 25, 26, 27, and 28.

Additionally, the system provides for a data rate of 320 megabytes persecond for data transfer.

It will be noted that data availability is possible for any of the portsat any particular time. Additionally there is provided a "wait period"for each port so that there will be "fairness" of access of data betweenthe ports so that one port will not monopolize all the access time butthat the access time will be distributed among the four ports.

Thus the multiport buffer 24 (of FIGS. 1, 2, 3, and 4) permits thesimultaneous transfer from buffer memory to each of the ports and fromeach of the ports to the buffer memory in any buffer memory locationincluding the very same location on a different system cycle.

The "system cycle" described herein is based on a 20 megahertz clocktime which provides for a 50 nanosecond system cycle.

The "command cycle" involves the initiation of an instruction by hostcomputer 4 until the completion of the cycle is signalled by the receipt(by host 4) of a "status signal" indicating completion ornon-completion.

Major significant features of the buffer memory system in each of theinterface controller boards (CIM, DIM) may be listed as follows:

(1.) All of the memory chips used in the buffer memory system are singleported static RAMs which are generally less expensive, more dense inholding information, and spatially smaller than multiport static RAMs.

(2.) The buffer memory system has 4 ports where each port has a datawidth of 36 bits, which constitutes a data word.

(3.) Each one of the 4 ports has the ability to access any location inany one of the memory modules of the buffer memory system.

(4.) The maximum "wait" for any first access of the buffer memory tooccur is 350 nanoseconds. Subsequently, access to the concatenatedfollowing words will be at a rate of 80 megabytes per second for theentire data burst length.

(5.) The "burst length" can be from 1 word alone to a maximum of theentire size of the allowable buffer memory which is 64 megabytes.

(6.) The address unit 24a has its address input bus at a width of 24bits which can address a maximum of 2²⁴ =16,777,216 words (4 bytes each)for a total of 16,677,216×4=67,108,864 bytes (64 Mega bytes).

The operation of the buffer 24 is illustrated in FIG. 8 which issubdivided into sections as FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D.

The left-hand column in each case shows the ports which are designatedas Port 0, Port 1, Port 2, and Port 3. These correspond to the portsshown in FIG. 3 which show the address ports 0A, 1A, 2A, and 3A, and inFIG. 2 as ports 26, 27, 28 and 25 respectively.

The top row of FIG. 8 shows the various buffer memory modules 24_(m0),24_(m1), 24_(m2), and 24_(m3) which have been designated in FIG. 8 asModule 0, Module 1, Module 2, and Module 3.

The "shaded portion" in each case shows how each port is connected to aparticular module and also shows the particular function that isoccurring.

Referring to FIG. 8A, it will be seen that Port 0 (0A, 0D, 26) (FIG. 3)is connected to Module 0 for the purpose of "accessing" a buffer memorylocation.

At the same time, it will be seen that Port 1 (1A, 1D, 24) (FIG. 3) isconnected to Module 1 for the purpose of accessing a location in buffermemory 24.

Likewise in FIG. 8A, the Port 2 (2A, 2D, 28) (FIG. 3) is seen connectedto Module 2 for the purpose of accessing a buffer memory location.

In FIG. 8A, the Port 3 (3A, 3D, 25) (FIG. 3) is connected to Module 3for the purpose of accessing a memory location.

Concurrently and simultaneously all the functions of FIG. 8A happen inone system cycle. In the next system cycle after FIG. 8A, the buffer isin position of FIG. 8B and similarly the buffer operations in thefollowing system cycles are shown in FIGS. 8C and 8D.

In FIG. 8B, (second system cycle), it is seen that Port 0 (FIG. 3) isconnected to Module 1 for accessing a data location; then Port 1 isaccessing Module 2 for a data location function. Similarly Port 2 isaccessing Module 3 as a data location function, and likewise Port 3 isaccessing Module 0 as a data location function.

It may be noted that in FIG. 8A, while Port 0 is accessing Module 0,then at the same time Port 1 is performing a WRITE operation on Module0, and an increment operation on Module 3, and Port 2 is performing anincrement operation (address counter increment) on Module 0 while alsodoing a Write operation to Module 1, and similarly in FIG. 8A, Port 3 issimultaneously performing a READ operation from Module 0.

Likewise as can be seen from FIGS. 8B, 8C, and 8D, various ones of thePorts 0, 1, 2, 3, are connecting to the various memory Modules 0, 1, 2,and 3 for purposes of performing access operations, READ operations, andWRITE operations, and increment (address counter increment) operationsduring the very same system cycle.

Referring to FIG. 9, there is shown a typical example for theAccess-READ function, for example, as accomplished by the Port 0 of FIG.8. At the left-most column of FIG. 9 there is shown a series ofaddresses to be used to access locations in various modules of thebuffer memory 24.

The second column at the left shows various time periods (system cycles)from time 0 thru time 21. This indicates the function that is occurringat any given time period in this example, wherein it is considered thatPort 0 (FIG. 8) is involved with various functions in the differentsections of Module 0, Module 1, Module 2, and Module 3.

Thus at Time 0 thru Time 5, it is seen that there is a "Wait", startingfrom Time 2, in which the address remains the same; and it is duringthis period of Time 0-5 that the Port 0 has an "Idle" function with theModule 0; has an "address latching" function with module 1 (Time 1); hasa "Wait" function with Module 2 (Time 2) and has a "Wait" function withModule 3 (Time 3).

In FIG. 9 it will noted that, at Time 5, the Port 0 (of FIG. 8) performsa READ function from Module 0, and then at Time 6, Port 0 performs aREAD function with Module 1; at Time 7, the Port 0 performs a READfunction with Module 2; and at Time 8, the Port 0 performs a READfunction with Module 3 and so on down through the various time periods.

Each of the time periods shown at the left hand column of FIG. 9represents a "system cycle" so that the time between the Time 0 and Time1 is one system cycle, or for example, the time between Time 10 and 11is a system cycle.

Another example is provided in FIG. 10 (Access-Write) in order to show,for example, how Port 0 (of FIG. 8) can concurrently and simultaneouslyperform access and WRITE functions with various ones of the buffermemory Modules 0, 1, 2, 3 (24_(m0), 24_(m1), 24_(m2), 24_(m3)).

At the left hand column of FIG. 10, there is the starting address atTime 1 shown as 0003F2. Then there is a "waiting" period up until Time 5where the address remains the same. After this period, the addresschanges (increments) at each succeeding time until at Time 19, theaddress is 000400.

Thus, using this example again of showing how the Port 0 connects tovarious ones of the buffer memory modules, it will be seen that variousIdle and Wait and Address Latch functions occur from Time 0 thru Time 4,but that at time period 5, the Port 0 now performs a WRITE function intoModule 2, and at Time 6, the Port 0 performs a WRITE function intoModule 3.

Likewise at Time 7, the Port 0 performs a WRITE function into Module 0,and at Time 8, the Port 0 performs a WRITE function into module 1, etc.

Thus the functionality of the buffer memory 24 is such, as shown inFIGS. 9 and 10, that there is concurrently and simultaneously, both"Reading" of data from various modules of the buffer memory by each ofthe ports and there is also the "Writing" into various modules of thebuffer memory by various ones of the ports.

FUNCTIONAL OPERATIONS

The peripheral storage devices (disk drives) and mass storage system ofFIG. 1 (which represents one-half of the overall system) provides thefunctions of Reading data from peripheral storage and Writing data intoperipheral storage. Additionally, each of these actions initiates aSTATUS operation to inform the main host computer 4 of the completion orincompletion of each Read/Write command.

As seen in FIG. 11, the steps R-1 through R-12 are involved for the Readand Status Operation.

Thus at step R-1, the Host 4 transmits a Read Command to the ChannelInterface Module (CIM) 8_(c1), or 8_(c2) (FIG. 1A).

In R-2, the protocol chip I-1, conveys this command to the interfacecontroller, IP_(c1) or IP_(c2) (FIG. 1A).

In step R-3, the interface processor (IP_(c1), IP_(c2)) transfers thecommand to the Buffer 24.

At step R-4, the control processor (10_(c1), 10c2) takes the ReadCommand from Buffer 24 and transmits the command through Future businterface FBi (31) to the Device Interface Module (DIM) 8_(d1), or8_(d2).

At step R-5, the Future bus interface FB1 (31) transfers the ReadCommand to the Buffer 24.

At step R-6, the DIM control processor (10_(d1) or 10_(d2)) sends theRead Command, through interface processor IP_(d1), IP_(d2) and thedevice interface D₁ (D_(1a), D_(1b), D_(1c), D_(1d)) to the peripheralstorage Disk Drive 70.

At step R-7, the Disk Drive 70 "Reads" the requested data from disk andgenerates a status signal. The data and status signal are transmitted,via device interface D1 (D_(1a), D_(1b), D_(1c), D_(1d)) and interfacecontroller IP_(d1) or IP_(d2), to the Buffer 24 (DIM) (24_(d1) or24_(d2)) (FIG. 1A).

At step R-8, the DIM control processor 10d (10_(d1) or 10_(d2)) performsa "status check" to see that the proper data was retrieved.

At step R-9, the DIM control processor 10_(d) transmits the checked-outdata and the status information, via Future bus interface FB₂ (32) tothe Channel Interface Module CIM (8_(c1) or 8_(c2)).

In step R-10, the Future bus interface FB2 (32) continues to implementstep R-9 by placing the data and status information in the CIM buffer24c (24_(c1), and 24_(c2)).

At step R-11, the CIM control processor 10c (10_(c1) or 10_(c2)) takesthe data and status information from the buffer 24 (24_(c1) or 24_(c2))and conveys it to the interface controller (IP_(c1) or IP_(c2)).

Then at step R-12, the CIM interface controller (IP_(c1) and IP_(c2))transmits the accessed data and status information via the protocolinterface (I-1, or I-2) to the host computer 4.

Now referring to FIG. 12, there is seen a flow chart illustrating thesteps involved in a WRITE operation to an addressed peripheral disk unit70 (70a . . . 70d, etc.).

At step W-1, the Host processor 4 (4a . . . 4d) sends a WRITE commandwhich includes the data to be written and also the address of the diskand its cylinder and sector. This command and data is conveyed to theChannel Interface Module (CIM 8_(c1) or 8_(c2)).

At step W-2, the (CIM) protocol chip (I-1, I-2) receives the command anddata for transmittal to the interface processor (IP_(c1), IP_(c2)).

At step W-3, the interface processor (IP_(c1), IP_(c2)) transfers theWrite Command and data to the Buffer 24c (24_(c1) or 24_(c2)).

At step W-4, the CIM Control Processor (10_(c1), or 10_(c2)) sends theWrite Command and data, via the bus 12₃ (FIG. 2), over the Future businterface FB (FB1, 31; FB2, 32) to the device interface module, (DIM8_(d1), 8_(d2)).

In step W-5, the Future bus interface (31, 32) in the DIM module(8_(d1), 8_(d2)) (FIG. 2) transfers the Write Command and data to theDIM buffer (24_(a1), 24_(a2)).

Then at step W-6, the DIM control processor (10_(a1), or 10_(a2)) sendsthe Write Command and data to the addressed disk unit 70 (70a . . . 70d)by routing it through the interface processor (IP_(d1) or IP_(a2)) overto the device interface D1 of the DIM.

At step W-7, the selected disk drive unit (70 etc.) writes the data intothe addressed cylinder and sector then sends a "Status" signal (toindicate completion) to the DIM Buffer 24d (24_(d1), 24_(d2)). This isdone via the DIM device interface D₁ and the interface processor(IP_(d1), IP_(d2)).

In step W-8, the DIM control processor (10_(d1), or 10_(d2)) checks the"status" signal for completion of the Write Command.

At step W-9, the DIM control processor (10_(d1), 10_(d2)) transmits thestatus signal information to the Channel Interface Module, CIM (8_(c1)or 8_(c2)) by routing through the DIM Future bus interface (FB₁, 31)(FB₂, 32) and the CIM Future bus (FB₁, 31) interface (FB₂, 32).

At step W-10, the Future bus interface (FB₂, 32) transmits the statusinformation to CIM Buffer (24_(c1), 24_(c2)).

At step W-11, the CIM control processor (10_(c1), 10_(c2)) accesses theCIM Buffer (24_(c1), 24_(c2)) and transfers status to the CIM interfaceprocessor (IP_(c1), IP_(c2)).

At step W-12, the CIM interface controller (10_(c1), 10_(c2)) transmitsthe status information (command complete or not complete) via the CIMinterface protocol unit (I-1, I-2) to the host computer 4 (4a, 4b,4c,4d).

The described mass storage system is seen to use a highly efficientbuffer memory system in the channel interface modules and deviceinterface modules. An Address Transfer System and a Data Transfer Systemof buffer memory provides four input/output ports to each interfacecontroller module (CIM, DIM).

This arrangement makes it possible for any one of the multiple ports tofunction on a Read operation, a Write operation, or a status operationsimultaneously with activities occurring on each of the other ports. Asa result of this, there is a "fairness" or equality of access among theports to the memory modules and also a high speed series of datacommunication and data transfer operations which can occur in thesystem.

While the concepts discussed in the buffer memory involved the use offour ports and four memory modules, the same concepts can lendthemselves for expansion on a larger scale without any loss of speed.For example, a scaled up version could involve 16 ports for the buffermemory system which would include 16 separate memory modules. In thisconfiguration, all the advantages of low power dissipation, minimalamount of board space, rapidity of data transfer and simultaneity ofReading and Writing operations could still be operative and functionalwithout any loss in speed compared to the four port system.

Described herein has been a highly reliable, transfer rate efficient,system for storage and retrieval of massive amounts of data usingvarious types of peripheral storage devices such as disk, tape, opticaldrive, and cache memory.

A single host system or plurality of host systems may be connected to aplurality of channel interface modules (CIMs) which carry commands anddata between the host system and a dual set of Futurebus interfacelines. Additionally connected to the Futurebus interface lines is aperipheral device interface module (DIM) which provides control andinterconnections between the peripheral storage devices and theFuturebus interface lines of the channel interface module (CIM). Each ofthe controllers of the channel interface module and the device interfacemodule is provided with a buffer memory system having multiple memorymodules and multiple ports which permit simultaneous and concurrentreading and writing of data with a highly rapid massive data transfercapability.

Additionally each of the modules in the subsystem is provided with livereplacement and redundancy capability such that any failure of a singleunit will be taken over by an additional redundant unit until such timeas repairs or corrections have been made to the faulting unit.

While one preferred embodiment of the system concept has been describedherein, other configurations based on the concept may also beimplemented yet be encompassed by the following claims.

What is claimed is:
 1. A system for high speed storage/retrieval ofmassive amounts of data on peripheral devices comprising:(a) hostcomputer means for commanding execution of storage/retrieval functionsto/from a plurality of peripheral devices and for selecting viable datacommunication pathways via selected ones of a plurality of firstcontroller interface means, dual bus means and a plurality of secondcontroller interface means; (b) said plurality of first controllerinterface means for control and management of said host computer meanscommands, each said first controller interface means including:(b1)first buffer memory means for holding data in transit between said hostcomputer means and said peripheral devices and including:(b1a) M portmeans connected to M memory modules for enabling access to any addresslocation in any one of said M memory modules and enabling simultaneousread and write operations into and out of any one of said M memorymodules, said M port means connecting said host computer means to saiddual bus means; (c) dual bus means for enabling communication betweensaid plurality of first controller interface means and said plurality ofsecond controller interface means; (d) said plurality of secondcontroller interface means receiving commands from said first controllerinterface means, and for selecting a peripheral device for data transferoperations each said second controller interface means, including:(d1) asecond buffer memory means which physically duplicates the M ports and Mmemory modules of said first buffer memory means and which connects saidperipheral devices to said dual bus means; (e) said plurality ofperipheral devices for storing massive amounts of data and wherein eachperipheral device has two ports each of which is connected to adifferent one of said second controller interface means.
 2. The systemof claim I wherein said first controller interface means includes:(a)means to enable host commands, data and status messages for temporarystorage and transfer between said host computer means and said dual busmeans.
 3. The system of claim 3 wherein said second controller interfacemeans includes:(a) means to temporarily store and transfer hostcommands, data and status messages between selected peripheral storagedevices and said dual bus means.
 4. The system of claim 1 wherein saidhost computer means includes:(a) a plurality of host computer units eachof which is connected to said first controller interface means; (b) aplurality of said first controller interface means wherein each one ofsaid first controller interface means includes:(b1) connecting means tosaid dual bus means; (b2) means to reconfigure communication through asingle bus after detecting failure of the other bus in said dual busmeans.
 5. The system of claim 1 wherein said dual bus means includes:(a)means to provide a multiplicity of communication channels between anyone of said plurality of first controller interface means and any one ofsaid plurality of second controller interface means wherein saidcommunication channels transfer data concurrently and simultaneouslybetween said first and second buffer memory means.
 6. A high speedstorage/retrieval system comprising;(a) host computer means forinstructing execution of data storage/retrieval operations; (b) firstinterface means for temporary storage of instructions, data and statusinformation and transferring information between said host computermeans and a dual bus means, said first interface means including;(b1) aplurality of duplicate units of said first interface means connected tosaid dual bus means; (c) said dual bus means providing parallelredundant data transfer channels between said first interface means anda second interface means; (d) said second interface means for temporarystorage of said instructions, data and status information and enablingcommunication transfers to/from selected peripheral storage devices,said second interface means including:(d1) a plurality of duplicateunits of said second interface means connected to said dual bus means;(e) wherein each said first and second interface means includes a buffermemory means having M ports; (f) said buffer memory means for temporarystorage of commands and data in M memory modules and including:(f1) Mports for enabling simultaneous Read and Write operations through said Mports.
 7. The system of claim 6 wherein said host computer meansincludes:(a) means to detect a malfunctioning bus and malfunctioninginterface means in said system; (b) means to reconfigure said system toenable an operable first or second interface means and an operable busbus in said dual bus means to execute the functions of anymalfunctioning bus and/or interface means.
 8. The system of claim 7wherein said first and second interface means each include:(a) errorchecking means in said plurality of first and second interface means forreporting malfunctions to said host computer means when any one of saidplurality of first interface means or second interface means or bus insaid dual bus means is inoperative.
 9. A system for enabling datatransfers between a host computer means and a plurality of peripheraldevices while providing redundancy and universal interconnectivity, saidsystem comprising:(a) a plurality of channel interface modules forproviding a plurality of data transfer channels between a plurality ofdevice interface modules and said host computer means; (b) a pluralityof device interface modules for providing a plurality of data transfermeans between said plurality of channel interface modules and saidplurality of peripheral devices; (c) dual bus means connecting each ofsaid plurality of channel interface modules to each of said plurality ofdevice interface modules; (d) wherein each of said channel interfacemodules and each of said device interface modules includes;(d1) amultiported buffer memory means having M ports for temporary storage ofdata in transit and which includes:(d1a) a plurality of M internalmemory modules; (d1b) means for distributing any incoming address toeach of said M ports concurrently; (d1c) means for simultaneouslyreading from or writing to any one or all of said M internal memorymodules. (d2) checking means to detect any malfunctioning bus orinterface module for signalling said host computer means: (e) said hostcomputer means including a plurality of host computers connected to saidchannel interface modules wherein each host computer includes:(e1) meansto detect a malfunctioning bus or malfunctioning interface module;(_(c2)) means to select a viable communication pathway for data transferoperations to said peripheral devices.
 10. In a network for enabling "M"host computer means to execute data transfer operation to/from aplurality of peripheral devices, a system for providing alternatemultiple paths between said host computer means and peripheral devices,comprising:(a) dual system bus means connecting a plurality of firstcontroller interface means to a plurality of second controller interfacemeans; (b) each said first controller interface means for managing thestorage and transfer of data between each pair of said host computermeans and said dual system bus means; (c) each said second controllerinterface means for managing the storage and transfer of data betweensaid dual system bus means and said peripheral devices; (d) wherein eachsaid first and second controller interface means includes:(d1) buffermemory means having M ports and M memory modules for enabling access toany address location in any one of said M memory modules and enablingsimultaneous read and write operations to/from each one of said M ports,said M ports providing connections to/from said dual system bus meansand to/from said host computer means or said peripheral devices; (d2)control processor means for sensing and utilizing any one of the viablecommunication paths facilitating said data transfer operations.